1. Field of the Invention
The present invention relates to an image recording method, and more particularly to a recording method of recording an image in a recording material that forms a color by irradiation of a laser beam.
2. Description of the Related Art
On beverage cans, beverage containers, food containers, medicine containers, cosmetics containers, packaging materials, electronic components, electric parts, automotive components and the like (hereinafter referred to as “containers”), a manufacturing lot number, manufacturing date, model, name of manufacturer and the like are, for example, marked by characters, symbols, marks, patterns, barcodes or the like (hereinafter referred to as “marks”).
As marking methods, a method of directly printing a colored printing ink on containers by pad printing, screen printing, an ink jet method or the like, and a method of attaching labels having marks printed thereon are used. In the direct printing method, however, printing may be difficult depending on the shape of the container to be printed on, and in the method of attaching printed labels, a wide variety of labels must be prepared for respective types of marks.
To solve these problems, recently, laser marking methods have come to be used in which a laser marking layer including a color former and a developer is provided on containers, and a laser beam is irradiated to the layer to cause a chemical reaction to form a color (see, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 7-257042, 2002-347344, and 9-175035). This method is superior in productivity to the previous methods and thus is suitable for forming marks on containers.
In the laser marking method, however, when printing a label coated with a laser marking layer, the label may be colored by the solvent of the printing ink, or when a container to which a label is attached is heated for sterilization, a color may be formed. As a result, if a laser is irradiated to form a color after this, clear marks may not be obtained, so that the commercial value is reduced.